JPH01224255A - Composite material and production thereof - Google Patents

Abstract

PURPOSE: To inexpensively obtain a high-strength composite material contg. desired ratios of a boride and carbide by making the heated melt of parent metal penetrate into a mass contg. boron carbide to react with it and to form the boride of the parent metal, then subjecting the parent metal to a carburization treatment to convert the remaining parent metal into a carbide.

CONSTITUTION: The parent metal (e.g.; Zr or Ti) is heated to a temp. above its m.p. in an inert atmosphere to form the molten parent metal body. The molten parent metal body is then brought into contact with the mass contg. the boron carbide and is penetrated into the mass, by which the molten parent metal is brought into reaction with the boron carbide and the boron-contg. compd. of the parent metal is formed. In addition, the penetration and the reaction are continued for a sufficient time, by which the self-supporting body contg. the boron-contg. compd. of the parent metal is produced. The self-supporting body is exposed to the carburization environment to convert the parent metal remaining in the self-supporting body to the carbide of the parent metal, to obtain the composite material.

COPYRIGHT: (C)1989,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides ZrB2-Zr by using carburizing method.
The present invention relates to a new method of manufacturing composite bodies, such as C-Zr composite bodies, and to new products made by such a process. More particularly, the present invention relates to one or more boron-containing compounds (e.g., borides or borides and carbides) formed by reactively infiltrating a molten parent metal into a bed or mass containing boron carbide. ) and optionally one or more inert fillers.

BACKGROUND OF THE INVENTION In recent years, there has been increasing interest in using ceramics for structural applications that traditionally were metals. This interest is due to the superiority of ceramics over metals in several properties such as corrosion resistance, hardness, abrasion resistance, elastic modulus, and heat resistance.

However, a major limitation to the use of ceramics for such purposes is the ease and cost of manufacturing the desired ceramic structure. It is well known to produce boride ceramic bodies by methods such as hot pressing, reactive sintering, reactive hot pressing, and the like. Although some success has been achieved with the methods described above in producing boride ceramic bodies, there is a need for a more effective and economical method of producing dense boron-containing compounds.

Additionally, a second major limitation to the use of ceramics in structural applications is that ceramics lack toughness (ie, damage tolerance or fracture resistance). This lack of toughness can cause ceramics to rapidly and easily become severely damaged in applications where relatively mild tensile stresses are present. This lack of toughness is also common in monolithic boride ceramic bodies.

One way to overcome the problems described above is to use ceramics in combination with metals, such as cermets or metal matrix composites.

The aim of such known methods is to obtain the best properties of the ceramic (
e.g. hardness or stiffness) and the best properties of the metal (e.g. ductility)
The goal is to obtain a combination of Although some success has been achieved in the production of borides in the cermet area, there is a need for more efficient and economical methods of producing boride-containing materials.

RELATED PATENT APPLICATIONS Many of the above-described problems relating to the manufacture of boride-containing materials are addressed in U.S. Patent Application No. 073, filed July 15, 1987, and assigned to the same assignee as the present applicant.
, No. 533.

The following definitions were used in the above-mentioned US patent application Ser. No. 073.533 and apply equally to this application.

"Parent metal" means a metal (e.g., zirconium) that is a polycrystalline oxidation reaction product, i.e., a precursor to a parent metal boride or other boron compound of the parent metal, and is pure or relatively pure. When a particular metal is referred to as a parent metal (e.g. zirconium), it is specifically Unless otherwise specified, such definitions shall be used.

"Parent metal boride" and "parent metal borocompound" refer to boron-containing reaction products formed by the reaction between boron carbide and parent metal; It includes the original compound and ternary or more original compounds.

"Parent metal carbide" means a carbon-containing reaction product formed by the reaction of boron carbide and a parent metal.

To briefly summarize the disclosure of the aforementioned U.S. patent application Ser. is manufactured. In particular, a bed or mass of boron carbide is penetrated by molten parent metal;
The boron carbide bed may consist entirely of boron carbide, thereby forming a self-supporting body containing one or more boron-containing compounds of the parent metal, the boron-containing compounds being borides of the parent metal, or both, and typically contains a carbide of the parent metal. It is also stated that the mass of boron carbide to be impregnated with the molten parent metal may also contain one or more inert fillers mixed with the boron carbide. Therefore, by combining an inert filler, a composite body is formed with a matrix formed by reactive infiltration of the parent metal, where the matrix contains at least one boron-containing compound, and where the matrix contains at least one boron-containing compound; It contains a parent metal carbide, and the matrix is embedded with an inert filler. Furthermore, in any of the embodiments described above (i.e., embodiments with fillers and embodiments without fillers), the final composite body contains residual metal as at least one metal component of the original parent metal. may contain.

Broadly speaking, the method described in the aforementioned U.S. patent application Ser. It is molten and placed adjacent to or in contact with a mass of molten metal or alloy. The molten metal penetrates the boron carbide mass and reacts with the boron carbide to form at least one reaction product. The boron carbide is at least partially reduced by the molten metal, thereby forming parent metal boron-containing compounds (eg, parent metal borides) and boro compounds under the temperature conditions of the process. Further, typically, a carbide of the parent metal is formed, and in some cases, a borocompound of the parent metal is formed. At least a portion of the reaction products are maintained in contact with the molten metal, and the molten metal undergoes wicking,
That is, it is attracted and transported toward unreacted boron carbide by capillary action. The metal thus transported forms additional borides, carbides, or borocompounds of the parent metal;
Formation of the ceramic body continues until the parent metal or boron carbide is completely consumed or the reaction temperature is changed to a temperature other than the reaction temperature.

The structures formed may include one or more borides of the parent metal, borocompounds of the parent metal, carbides of the parent metal, metals (such as alloys or intermetallic compounds as described in the aforementioned U.S. Patent Application No. 073,533). compounds), pores, or any combination thereof.

Furthermore, these several phases may be connected to each other in one or more dimensions throughout the composite body;
Further, they may not be connected to each other. By varying one or more conditions such as the initial density of the boron carbide body, the relative amounts of boron carbide, the parent metal, and the alloy of the parent metal, the amount of filler within the boron carbide, temperature, and time; The final volume fraction of boron-containing compounds (ie, borides and borocompounds), carbon-containing compounds, and metal phases can be controlled.

The typical environment or atmosphere used in the aforementioned US patent application Ser. No. 073,533 was relatively inert or non-reactive under the process conditions. In particular, it is stated that, for example, argon gas or vacuum are preferred process atmospheres. Furthermore, it is stated that when zirconium is used as the parent metal, the resulting composite material contains zirconium diboride, zirconium carbide, and residual metallic zirconium. Also, when aluminum as the parent metal is used in the process described in the aforementioned US patent application, A13B48C2, A I
It is described that a borocarbide of aluminum such as B C or AlB24C4 is formed, leaving aluminum as the parent metal and other unreacted, unoxidized components of the parent metal. Other parent metals described as suitable for use in the process conditions of the aforementioned US patent applications include silicon, titanium, hafnium, lanthanum, iron, calcium, vanadium, niobium, magnesium, and beryllium.

Thus, the aforementioned U.S. Patent Application No. 073,533 includes:
A new method and new materials formed by the new method are disclosed that overcome many of the deficiencies of the prior art discussed above and thereby satisfy long-standing needs.

SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned problems of the prior art and to solve these problems.

The present invention provides a method for modifying the amount of parent metal present in a composite body. In particular, the amount of parent metal can be modified or controlled by exposing the composite body (and thus the residual parent metal in the composite body) to a carburizing environment (e.g. gaseous carburizing species or solid carbon material), whereby the carburizing environment removes the residual parent metal. The composition is modified, thereby modifying the properties of the remaining parent metal. Furthermore, the properties of the composite body formed are also modified. Parent metals such as zirconium, titanium, and hafnium are well suited to be treated by the carburizing process of the present invention. In this application, ZrB, hereinafter referred to as ZBC composite material body
A 2-ZrC-Zr composite body will primarily be described. Although ZBC composite bodies are specifically described, similar manufacturing processes may be applied to composite bodies having titanium or hafnium as parent metals.

Broadly, after the ZBC composite is formed according to the method described in the aforementioned U.S. Patent Application No. 073,533,
The ZBCI composite is embedded within a bed of graphite or carbon donor material contained within a refractory container made of gold material. Then ZB
The refractory container filled with the C composite material and the bed is heated, for example, in a resistance electric furnace with an argon atmosphere. A small amount of H, O or Or! during heating. It is thought that the molecule becomes available for reaction. Such small amounts of H, O, and O2 are naturally present in the argon gas or are released from the graphite bed or ZBC composite. Thus, when the ZBC composite is heated, the carbon within the graphite bed reacts with oxygen to form gaseous carburizing species. For example, a mixture of CO and CO2 or H
A direct source of carburizing species may be provided, such as a mixture of : and CHA. Carbon from the carburized species is dissolved into the ZrC phase in the ZBC composite, and the carbon is then transported throughout the ZBC composite by a pore diffusion-x mechanism. The carbon is thus transported to contact the remaining parent metal to form an additional carbide phase of the parent metal (for example, if zirconium is the parent metal, a ZrC phase is formed by the carburizing process). A portion of the carbon from the bed of graphite is diffused directly into the Z r Ct□ phase.

Such carburization is advantageous because it allows the residual parent metal phase to be converted into, for example, a harder and more heat-resistant phase. Especially in applications where high temperature strength is required, ZB
C composites begin to lose strength at temperatures at or above the melting point of the residual parent metal phase. By post-processing with the ZBCI composite gold material process, the parent metal phase is converted to a carbide of the parent metal (for example, zirconium as parent metal is converted to ZrC). Referenced U.S. Patent Application No. 07
ZB manufactured according to the method described in No. 3,533
The amount of parent metal remaining in the C composite material is approximately 5 to 40 vol.
%. By exposing ZBC composite material to carburizing species,
The amount of zirconium as residual parent metal is e.g.
Reduced to vo1%.

The modified ZBC composite material is useful for aerospace components such as nozzle inserts. This is because the low metal content increases the high toughness and thermal shock resistance of ZBC composites (without sacrificing them).
This is because composite materials can be used. Thus, the carburizing treatment of the present invention is suitable for applications requiring high temperature erosion resistance, good thermal shock properties, and relatively high high temperature strength at temperatures of, for example, 2000 to 2700°C. Particularly applicable.

Furthermore, since the carburizing process of the present invention is time dependent, ZB
A carburized region, ie a carburized surface phase, can be formed on the C composite body. The wear resistance of the ZBCI composite body can thus be improved while ensuring that the interior of the ZBC composite material has a high metal content and therefore a high fracture toughness. Such ZBC composite bodies are particularly applicable to the manufacture of wear plates, wear rings, impeller inserts for various industrial pumps that are subject to corrosion and turbulence. In particular, metallic zirconium has very high corrosion resistance against strong acids, but the wear properties of the metal itself are not good.

Thus, by using the ZBC1i composite material, a ceramic outer surface having excellent wear resistance can be formed around the ZBC composite material having corrosion resistance. Furthermore, if substantially all of the metallic zirconium is converted to the Z'C1-8 phase and carburization is continued, the carbon content in the ZrC1-X phase can be increased (e.g. from about ZrC to about ZrC).
0.58 0.98 ) It is believed that when such a conversion is induced, the hardness and heat resistance of the ZBC composite improve.

The method of the present invention and the novel composite bodies produced by the method of the present invention thus further extend the uses of ZBC composite bodies.

The present invention will be described in detail below with reference to examples.

EXAMPLES The present invention provides post-processing techniques for the properties of ceramic composite bodies, particularly those produced by reactive infiltration of zirconium, hafnium or titanium as parent metal into a mass of boron carbide. This is based on the discovery that it can be modified by a carburizing process. The carburizing process changes the microstructure and thus the mechanical properties of some or substantially all of the ZBCI composite body.

A ZBC composite body manufactured in accordance with the aforementioned US patent application Ser. No. 073,533 is modified by exposing the composite body to a gaseous carburizing species.

embedded within the bed and produced by reacting at least a portion of the graphite bed with moisture or oxygen in a controlled atmosphere furnace. However, the atmosphere in the furnace must contain a non-reactive gas such as argon as a main component.
Matheson Gas products.

Favorable results are obtained by using argon gas supplied by Inc. It is not clear whether the impurities present in the argon gas provide the necessary O2 to form the carburized species, and the argon gas may be generated by evaporation of the graphite bed or the constituent aspects of the components within the ZBC composite body. It is also unclear whether it acts only as a carrier containing impurities. Furthermore, the gaseous carburizing type is ZB.
C may be introduced directly into the controlled atmosphere furnace during heating of the composite body.

When the gaseous carburizing species is introduced into the controlled atmosphere furnace, the gaseous carburizing species may contact at least a portion of the surface of the ZBC composite body embedded in the loosely packed graphite powder. The layup must be designed accordingly. The carbon in the carburizing species and the carbon from the graphite bed are dissolved in the mutually connected zirconium carbide phase, and the zirconium carbide phase is dissolved into the ZBCm composite material by a vacancy diffusion process if necessary. The diffusion of carbon into the remaining parent metallic zirconium is very slow. Thus, in the absence of a zirconium carbide phase, all remaining metallic zirconium in the ZBC composite body It would be impractical or uneconomical to dissolve the carbon into the zirconium carbide phase because it would take a very long time.The diffusion of carbon into the zirconium carbide phase and the diffusion of carbon into the metallic zirconium phase are both time dependent. However, the transport rate of carbon in the zirconium carbide phase is much faster than that in the metallic zirconium phase.

When the desired amount of carbon is introduced into the ZBCI composite body and contacts the remaining parent metal zirconium, the parent metal zirconium is converted to ZrC. Such a transformation is desirable. This is because the ZBC composite thus modified has high hardness and elastic modulus with little loss of bending strength or toughness. Furthermore, since the ZBC composite metal content is reduced, the high temperature properties are also improved. 5～
The ZBC composite material containing 30vol% residual parent metal is carburized as a post-treatment to reduce the amount of parent metal remaining in the ZBC composite material to about 0 to 2vo1%, typically about 0.5%.
It was found that it could be modified to be ~2 vol%. Thus, substantially all of the parent metal (but typically about 4.5-28 vol. % parent metal) can be converted from zirconium to ZrC.

Additionally, by controlling the time that the ZBCI composite body is exposed to the carburizing species and the temperature at which the carburizing process occurs, a carburized region, ie, a carburized layer, can be formed on the outer surface of the ZBC composite body. This process creates a hard, wear-resistant surface surrounding a core of ZBC132 composite material with relatively high metal content and relatively high fracture toughness.

Briefly, a ZBC composite material, typically containing about 5 to 30 vol.% of residual parent metal zirconium, is heated in an argon atmosphere providing at least some moisture or oxygen.
Exposure to carburizing species in a controlled atmosphere furnace operating at temperatures of approximately 1500-2200° C. for a period of ~48 hours has shown that the ZBC1fi composite material becomes a more desirable composite body than the carburized material. Ta.

The example below is an example of the present invention, which includes a composite body,
This is particularly intended to explain various aspects of carburizing treatment as a ZBCf2 composite material composite material, and is not intended to limit the scope of the present invention.

EXAMPLE A ZBC composite body was prepared according to Example 1 described in US Patent Application No. 073,533. The left column of Table 1 below shows various mechanical properties of the ZBC composite bodies thus formed. All sides of the ZBC composite body were then degreased using ultrasound in acetone and ethanol. The ZBC composite body was then embedded in a bed of high purity graphite powder having an average particle size of approximately 75μ. The graphite powder was sold by Lonza, Inc. and had the trade name KS-75. A bed of graphite powder was stored in a graphite mold (Grade ATJ sold by Union Carbide). A graphite cover plate was then placed on top of the mold. The assembly, including the ZBC composite body embedded in graphite powder, was then placed in an atmosphere-blocked resistance heating furnace. The atmosphere inside the furnace is Matheson Gas Products.
, Inc.

The argon was supplied by The furnace was first evacuated to 1X10-'Torr at room temperature and then filled with argon. The furnace was then evacuated to a pressure of 1X10-'' Torr and heated under vacuum to a temperature of approximately 500°C. The furnace was then again filled with argon at a flow rate of approximately 1. It was kept flowing and maintained at a pressure of about 2 psi (140 g/cd). The furnace was then heated to a temperature of about 1750 °C over 6 hours and then maintained at 1750 °C for about 12 hours. The furnace was then heated to a temperature of about 1750 °C for about 12 hours. It was cooled for about 6 hours. Z was carburized after cooling.
The BC composite was removed from the furnace and excess graphite powder was removed by grid blasting.

The right column of Table 1 below shows the ZB after carburizing treatment.
C shows the mechanical properties of the composite material.

The amount of residual parent metal zirconium is less than about 10vol% and about 0%.
．． 5 vo1%, hardness, elastic modulus,
It can be seen that both shear coefficients are increasing.

However, the bending strength is sacrificed to some extent, but it is approximately 500
The bending strength of M Pa is sufficient for many aerospace applications.

Table 1 Before carburizing After carburizing Zn content jl (vo1%) 9.9 0.5
Hardness (HRA) 80.6 81.9 (HK
) 10i1 1388 Modulus of elasticity (GPa
) 364 442 Shear modulus (GPa)
158 1844 point bending strength (MPa) 8
75 497 Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to such embodiments, and various other embodiments may be employed within the scope of the present invention. It will be obvious to those skilled in the art that this is possible.

[Brief explanation of the drawing]

FIG. 1 shows a bed 2 of graphite powder to be treated according to the present invention.
1 is an illustrative cross-sectional view showing a ZBC composite material body 3 embedded within and housed within a fireproof container 1; FIG. 1...Fireproof container, 2...Graphite powder floor, 3...Z
BC composite material patent applicant: Lanxide Technology Company, L.P.

Claims (2)

[Claims] (1) A method for manufacturing a self-supporting body comprising manufacturing a first composite material body, comprising the steps of selecting a parent metal, and heating the parent metal at a temperature above its melting point in a substantially inert atmosphere. heating to a temperature to form a molten parent metal body and contacting the molten parent metal body with a mass containing boron carbide; and infiltrating the molten parent metal into the boron carbide mass to bring the molten parent metal into contact with the boron carbide mass. maintaining said temperature for a sufficient period of time to react with boron carbide, thereby forming at least one boron-containing compound; and producing said self-supporting body comprising at least one boron-containing compound of a parent metal. and exposing the self-supporting body to a carburizing environment, thereby converting the parent metal remaining in the self-supporting body to a carbide of the parent metal. manufacturing methods including. (2) A metal layer selected from the group consisting of zirconium, titanium, and hafnium and present in an amount of substantially 0.5 to 2 vol%, and a three-dimensionally interconnected ceramic phase extending to the boundary. , the ceramic phase includes a carbide selected from the group consisting of a zirconium carbide, a titanium carbide, and a hafnium carbide, and further includes a metal boride corresponding to the carbide, the boride having a platelet shape. A composite material with a structure of